FR2589261A1 - PNEUMATIC INTERFACE APPARATUS - Google Patents

Abstract

THIS INTERFACE APPARATUS HAS PNEUMATIC FLOW CONTROL MEANS FOR CONTROLLING THE NUMBER OF MOLES OF A GAS CONTAINED IN A VOLUME OF GAS SUBSTANTIALLY CONSTANT IN A FIRST CHAMBER 61 AND A SECOND CHAMBER 65 ISOLATED FROM ONE ANOTHER OF THE OTHER. WHICH CONCERNS THE FLOW OF THE FLUID. THE VOLUMETRIC RELAY PROVIDES IN ITS SECOND CHAMBER A SECOND PRESSURE WHICH PRESENTS A PREDETERMINED RELATION WITH THE FIRST PRESSURE. A SUBSTANTIALLY CONSTANT CONTAINED VOLUME IS COUPLED WITH THE FLOW CONTROL MEANS AND THE RELAY AND FLOW CONTROL MEANS INCLUDING MEANS FOR ADJUSTING THE GAS FLOW RATE OF THE SUBSTANTIALLY CONSTANT VOLUME TO AN AREA WITH AMBIENT PRESSURE.

Description

258926i

PNEUMATIC INTERFACE APPARATUS

  Pneumatic control of treatment systems is widely used when installing systems requires robust components, reduced costs, ease of installation and troubleshooting, and a high degree of maneuverability. Examples of these systems that lend themselves well to pneumatic control include temperature control of refrigeration systems and boilers, control of steam or air line pressure, control of flow in systems of pipes carrying fluids, controlling the level of liquid in the tanks, controlling the pH in chemical processes, and controls for heating, ventilation and air conditioning. The pneumatic control is

  frequently used in petro-

  chemicals in which flammable fluids are often present and can be ignited by electrical controls. For the purposes of illustration, and not for the purpose of limitation, the invention is shown and described in relation to a heating system,

ventilation and air conditioning.

  Heating, ventilation and air conditioning systems (HVAC systems) are often used in buildings to control the temperature of a space

  air conditioned inside the building and for eco-friendly purposes

  energy. One type of HVAC system includes an air treatment unit having a plurality of moderators actuated by control devices to control the flow rate of the outside air to the building, to control the flow rate of the exhaust air of the building and to direct the air which is heated or cooled and which is recirculated. The other mechanisms associated with air treatment units generally include valves actuated by control devices to control the flow of chilled or heated water in heat exchange coils arranged in the distribution network.

  of air to control the temperature of the air circulating in it.

  A type of control device used with

  these air handling units have a pneumatic cylinder

  material tensioned by a spring, the piston of which is coupled with a moderator or a valve. The cylinder is connected to a pneumatic pressure source such as a network of pneumatic buses formed by flexible small diameter polyethylene tubes and installed throughout the building. Control takes place by solving known algorithms inside a pneumatic control device and by generating analog pneumatic output signals

directed towards the cylinders.

  The relatively recent arrival of

  direct digital computer control, as well as the desire of building owners to incorporate these computer devices into new or existing heating, ventilation and air conditioning systems, employing inexpensive and robust pneumatic controls,

  require the use of a digital interface system -

  pneumatic to receive digital signals from the device

  control board and translate them into pneumatic signals for positioning cylinders or other control devices. These direct digital control devices can be constructed and organized to solve

  repeatedly one or more computation algorithms

  known in order to generate control signals for the interface system, and, for reasons unrelated to the invention, it is often preferable to arrange the digital control device so that it delivers signals that order the cylinder to undergo a calculated change in pressure rather than coming to a new position, represented by a new absolute pressure. In other words, it is often preferable to design the digital control device and the

  system connected to it in such a way that the new po-

  sition which must be taken by a cylinder is a function of the duration of the digital output signal from the

  control rather than changing the cylinder pressure.

  In pneumatic control systems commonly

  bent, it may also be desirable that cylinders determined within the system perform a complete displacement for pressure ranges which may differ from one cylinder to another, the following pressure ranges being commonly used for a complete displacement 206.84 to 551.58 mb (3 to 8 psig), 551.58 mb to 896.32 mb (8

  at 13 psig) and 896.32 at 12zt, 1 mb (13 to 18 psig).

  An example of a useful interface system for

  request the position of a single co-control device or to simultaneously control the position of several control devices having sizes, pressure ranges for complete displacement and identical loads is described in US Patent No. 4,261,509. This system behaves

  a pair of electrically operated two-position solenoid valves

  to receive digital signals and to

  control the flow of fluid entering and leaving the dispo-

  ordering information. Pneumatic resistances9 sometimes

  called throttles, having passages which cross them

  sent, of a diameter generally measuring a few hundredths of a millimeter, are arranged in the pneumatic lines to control the distance of movement of the control devices per unit of time, that is to say to control the slopes of the pressure curves -time control devices, representing the movement characteristics

  control devices in their two directions of-

of displacement.

  Another example of an interface device is shown in US Patent No. 4,440,066, and includes a pair of solenoid valves for controlling the flow of air flowing from a pressurized source to a volume region indeterminate, and from that region to an area with ambient pressure. An adjustable flow passage is

  present to control the flow rate to and from

  shot of a control device connected to it, for example

  a cylinder. U.S. Patent No. 3,266,380 discloses the utility

  reading of a reservoir as a capacity for integration into a pneumatic calculation device, not suitable for control by interface, which admits variable inlet pressures, and which, like the apparatus of US Pat. No. 4,440,066 shown below above mentioned, includes a return device (loop

closed).

  If interface systems of the type mentioned above have so far been satisfactory for the positioning of control devices, they are not

  no less characterized by certain disadvantages. For example-

  ple, when using throttles to control

  the displacement characteristics of a

  single command or group of control devices having identical sizes, spring ranges and loads,

  the sizes of the choke passages must be determined

  mined by experimentation at the installation site. This is due to the fact that the travel times of the control devices are dependent on the size, the spring range and the load of the control devices, and on the volume of fluid contained inside the control device and pneumatic interconnections. These parameters are often difficult or impossible to determine before the actual installation. If the heating, ventilation and air conditioning system requires sequencing of the control devices and includes

  control having volumetric sizes, ranges of

  fate and / or different loads, the system will have highly non-linear gain characteristics, and the control problem will therefore be made even more complicated. If you use the interface system of the

  U.S. Patent No. 4,261,509 mentioned above, e.g.

  ple, and if it is assumed that it is necessary to control a plurality of control devices configured differently and con-

  connected in parallel, the percentage of change in posi-

  tion will be different for each control device for a given time during which a solenoid valve is actuated in order to introduce a fluid into the control devices or in order to evacuate a fluid. This results from the fact that a change in the volume of fluid contained by a control device will affect the distance of movement per unit of time of the other control devices according to the characteristic equation of an ideal gas. If throttles are selected to control the travel time of a small controller with a light load, for example, the system response will be far too slow to position larger or more heavily loaded controllers. On the other hand, if throttles are selected for the correct control of devices

  of the latter type, there may be ins-

  system tabilities. Even if a device called a pilot positioner is installed on some or all of the control devices, the selection of the throttles must still be made by field experimentation or by measurement and calculation of the volume of fluid compressed contained inside the pneumatic interconnections and the compression chambers of the pilot positioners.

  Another drawback of systems of the above type

  above mentioned is that they may be subject to significant pneumatic fluid leakage. For example, each pneumatic connection of 6.35 mm tubes has an average leakage rate of approximately 1.639 ml / min (0.1 cubic inch per minute) under a pressure of 1379 mb (20 psig), while a Characteristic pilot positioner has a leakage rate of 4,916 ml / min (0.3 cubic inch / min).

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  having a constant volume reservoir, in which the system contains a relatively small volume of fluid

  and / or a large number of connection and position points-

  pilot values, changes in control pressure due to leaks in the system and during the time between the measurement times of the parameters, for example between

  the moments of measurement of the temperature of a climatic space

  bet, would be far too important.

  Consequently, an interface system allowing the preselection of the sizes of the throttle passages independently of the configuration of the pneumatic bus and of the control devices concerned, which can be used to control control devices having a wide variety of volumes of fluid contained and which could have an adjustment device allowing its use with control devices which can operate on any one of several pressure ranges would represent

  a significant advance compared to the existing technique.

  In general, the interface device of the present invention comprises pneumatic flow control means for controlling the number of moles of a confined gas

  in a substantially constant volume of gas at a pre-

  better pressure. A volumetric relay has a first chamber coupled with the means of control by the volume of confined gas and a second chamber for coupling

  with a pneumatic control device to be com-

  mandé in position, the first chamber and the second chamber

  being isolated from one another with regard to the flow-

  fluid. The volumetric relay provides in its

  second chamber a second pressure which presents a re-

  predetermined lation with the first press. Means

  having a substantially constant confined volume are in-

  overlapped between the flow control means and the relay

  and cooperate with the flow control means to de-

  finish the slopes of the pressure-time curves of the device 7 z2589261

  control. The flow control means may include

  ter means for adjusting the gas flow rate from the substantially constant volume to an area at ambient pressure.

  An object of the invention is to provide an apparatus

  new and improved interface software for positioning

  pneumatic control devices which eliminates inconvenience

  of the existing technique.

  Another object of the invention is to provide a

  interface device which allows the preselection of foreign-

flow control sliders.

  Yet another object of the invention is to pro-

  Cure an interface device which ensures positioning characteristics of the control devices which are independent of the size or number of the control devices.

command connected on it.

  Another object of the present invention is also

  ment to provide an interface device which may include means for adjusting the range of the flow rate of a gas of a substantially constant confined volume towards a

room pressure area.

  Another object of the present invention is to provide an interface apparatus which is usable with direct digital control apparatuses. Another object of the present invention is still to provide a pneumatic interface apparatus which results in the movement of a control cylinder to a new position which is a function calculated from the duration of a digital signal from a direct digital control device. How these and other objects of the invention are accomplished will become apparent

  more clearly from the detailed description thereof

  ci, seen with the attached drawings.

  Figure 1 is a graphical representation of the described characteristics of increase and fall of the

  pressure within a substantial confined gas volume

partially constant;

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  Figure 2 is a simplified schematic representation showing the interface apparatus of the present invention in connection with an example of a treatment control system comprising an air treatment unit; Figure 3 is a block diagram of a first embodiment of the interface device shown in Figure 2, some parts being shown in section and other parts being shown in full; Figure 4 is a block diagram of a second embodiment of the interface device of Figure 2 with

  parties partially represented, parties represented

  smelled in section and other parts shown in full; Figure 5 is a cross-sectional view of the volumetric relay part of the interface device taken in plane 5-5 of Figure 3 and some parts of which are shown in external view; Figure 6 is a top plan view of a commercial embodiment of the apparatus of the invention; Figure 7 is a side elevational view of the apparatus of Figure 6, taken along the plane 7-7 thereof, with parts shown in section and other parts shown in external view; Figure 8 is a top plan view of the flexible lever of the apparatus of Figure 7; Figure 9 is a side elevational view of the lever of Figure 8, taken along the plane 9-9 thereof; FIG. 10 is a side elevation view,

  in section, of the central plate of the apparatus with par-

  parts added in exploded view; and

  Figure 11 is an electrical diagram of the apparatus

  reil. Understanding the invention will be facilitated by an explanation of the applicable gas law, and,

  in the field of applied physics, we express the equa-

  tion characteristic of an ideal gas in this form: pV = nRT in which: p = pressure of a gas in a substantially rigid volume or confinement container; V = confined volume of the container; n = number of moles of gas inside the container; R = universal gas constant; and T = gas temperature in K. It is clear from the equation that if the temperature of the gas confined in the container is kept constant, which is a reasonable assumption for this analysis, and if the volume of the container remains unchanged , the gas pressure will have a direct relationship with the number of

  moles of gas confined inside the container.

  The understanding of the invention will also be facilitated by the reference to the graph in Figure 1 which represents the characteristics of increase and fall

  gas pressure valid in a given volume of gas

  finished and substantially constant. Curve A represents the characteristic of pressure increase over time when a gas is introduced into the confined volume from a source at constant pressure,

  1379 mb (20 psig), for example, and by a passage of limi-

  tation of the determined flow. It is assumed that the mano pressure

  initial metric in volume is O mb. Curve B represents the characteristic of pressure drop over time when the compressed gas in the volume is allowed to be evacuated from the volume to a pressure zone

  ambient, for example to an area under mano pressure

  metric of O mb, the evacuation being done by a flow limiting passage of determined size. The control of gas flow to and from the volume can be ensured by a pair of two-position solenoid valves normally

closed.

  The curves A and B are neither linear nor the other, it is clear that if one wishes to actuate a cylinder on the range C from 206.84 to 551.58 mb (3 to 8 psig) , for example, the generally linear part of curve A which is in range C has a slope which is extremely different from that of the slightly arcuate part of curve B which is located in range C, when we ignore the algebraic signs of slopes. Therefore, with a cylinder pressure located within range C and increasing along curve A, the value of the change in pressure per unit of time is different from that of a decreasing cylinder pressure along of curve B and within range C. This can produce an unacceptable result if it is desired that the cylinder is controlled by signals from a digital control device with which the positioning of the cylinder is done. preferably by a calculated signal duration, rather than by measuring changes in pressure or by other means. On the other hand, the slopes of curves A and B in

  range D from 551.58 to 896.32 mb (8 to 13 psig) are substantial

  tally equal to each other if we ignore their signs

  algebraic, which shows that the particular passage uses

  read in the system on which the curves are based would probably be satisfactory for the operation of the cylinder with a digital control device in the

  range 551.58 to 896.32 mb (8 to 13 psig).

  If we then refer to Figure 2, the

  interface board 10 of the present invention is shown in connection with an example of a treatment control system comprising an air treatment unit 11 arranged to communicate with respect to the flow of the fluid with a space 12 to be air conditioned. The air treatment unit 11 comprises an inlet duct 13 for introducing outside ambient air into the space 12, an exhaust duct 14 for discharging the air, and a return duct 14a transversely connected coupled between the inlet pipe 13 and the outlet pipe

  14. Fans 15 are present to produce a

  forced air placement. Each pipe 13, 14, 14a comprises

  carries a mobile moderator 16 disposed inside it

  to control the flow of air passing through it. The inlet pipe 13 also comprises an air cooling coil 17 which is traversed by chilled water and an air heating coil 18 which is traversed by hot water or steam, the coils 17, 18 being provided to control the air temperature

  which is introduced into space 12. A water valve refri-

  managed 19 and a hot water valve 20 are coupled to the service

  cooling pin 17 and the heating coil 18, respectively, for modulating the flow rate of the liquids in the coils. The air processing unit 11 also includes pneumatic transducers for converting signals in another energy state, from a pneumatic signal to an electrical or mechanical signal, for example. By way of illustration, these transducers may include a plurality of control devices or pneumatic cylinders 21, each control device being mechanically coupled with its moderator 16 or its

  gated 20 associates in order to be able to control the position-

  ment of these. The transducers 21 can be coupled

  to a pneumatic bus (not shown) which provides pressure

  pneumatic pressure controlled to position the devices

  21 and the moderators 16 and the associated valve 20.

  A device for direct digital control of the system 27 is coupled to a device for communicating the parameters, such as a thermostat 29, so as to receive signals from

  this one. The system control unit 27 collects

  periodically a system parameter, for example the temperature

  erasure of the space transmitted by the thermostat 29, the com-

  counter with the reference value of the intro temperature

  pick and set up inside the database of his computer, symbolically represented by the arrow 31, numerically solves a command algorithm and generates

_______ _12 2589261

  digital electronic control signals for

  request a transducer position. For the purposes of illustration, the invention will be described in relation to a pneumatic cylinder 25 connected to the device 10 by a pneumatic bus 26, and it must be considered that the temperature is only one of several possible parameters of the treatment system, the control of which will be facilitated by the interface device 10 of the invention, and it will be appreciated that the latter can be used in systems for controlling treatments everywhere o pneumatic transducers

  are used to control the parameters.

  If we then refer to Figures 2 and 3, a

  first embodiment of the interface apparatus 10 is con-

  connected to an example of a pneumatic transducer comprising the cylinder 25 positioned pneumatically, tensioned by a spring, coupled with a pivoting air moderator 16 for controlling the positioning thereof. The apparatus 10 includes pneumatic flow control means 33 which can be coupled to a first source 35 of compressed fluid, such as an air compressor set to a pressure

  regulated, coupled to the first end 37 of a pneumatic bus

  tick 38 whose second end 39 is open for free discharge of the fluid into the atmosphere. Although the

  regulated pressure can be chosen according to the charac-

  téristics of the various components coupled on it, a pressure of the source of 1379 mb approximately (20 psig) is current for the control of the treatment of heating, ventilation and air conditioning systems. A pair

  solenoid valves normally closed, electrically controlled-

  ment, comprising a first inlet valve 41 and a second outlet valve 43, is arranged in series for

  control the flow of compressed fluid to and from the

  lume or substantially constant confined container 45 connected therebetween. Control electromagnets

  of the first valve 41 and of the second valve 43 have each

  cun their electrical conductors 47 coupled to the device

  control 27 of the system for receiving control signals

  command of it. The pneumatic flow control means 33 also comprise a plurality of chokes comprising a first choke 49 arranged in the bus in the vicinity of the first valve 41 and the second, third and fourth chokes 51, 53, 55, respectively, arranged in the end 39 adjacent to the second valve 43. Each restrictor 49, 51, 53, 55 has a passage or orifice

  longitudinal 57 passing through it to control the flow of

  compressed gas from or to the confined volume 45.

  When the first valve 41 is actuated, the first valve

  glor 49 will allow the fluid to flow in a res-

  embrace of the source 35 to the confined volume 45, while the control of the second valve 43 will allow the fluid to be evacuated from the confined volume 45 through the second choke 51, through the third choke 53 and / or

  the fourth throttle 55, and from there into the atmosphere.

  The restrictors 53 and 55 can be chosen so as to

  have fixed passage sizes that are substantial

  that are identical or that differ from each other

  in order to provide the desired flexibility in the application.

  The throttles 53 and 55 can be replaced by a choke

  adjustable vernier glor downstream of the solenoid valve 43, but this arrangement in principle requires calibration in the factory or in the field, which represents a procedure which can be costly. The chokes 53, 55 with fixed passage sizes can be installed in

  permanently or be of the plug-in and removable plug type.

  In another possible embodiment, the device 10 can also be made in such a way that the second end 39 has only one discharge point (not shown) having a single throttle, for example

  the choke 53, fixed inside of it.

  The selective control of the first valve 41 or of the second valve 43 therefore facilitates the regulation of a first pressure inside the confined volume 45. When neither the valve 41 nor the valve 43 are actuated, the pressure in the volume 45 remains substantially constant, for reasons explained in more detail below. It will be appreciated that the interface device 10 can operate both with a throttle 49, 51 located on the upstream side and on the downstream side of its associated valve 41, 43 in the bus 38, and that the choke locations indicated are simply

for illustration.

  Referring to Figures 3 and 5, the pneumatic flow control means 33 are coupled by a pneumatic bus 59 to the first input chamber 61 of a volumetric relay 63, the second output chamber of which is coupled by an output bus 67 to one or more

  transducers to be positioned, such as transducer 25.

  A second source 69 of compressed gas under a substantially constant pressure, for example 1379 mb (20 psig), is attached to the second chamber 65 to serve as a pneumatic actuating means for the transducer 25. The volumetric relay 63 comprises an elastic diaphragm 71 disposed between the first chamber 61 and the second chamber 65 to maintain the chambers 61, 65 isolated from one another as regards the flow of the fluid. The volumetric relay 63 is designed and constructed so that the pressure in the second outlet chamber 65, and therefore in the outlet bus 67 and in the transducer 25, have a predetermined relationship with the pressure in the first chamber input 61, regardless of changes in

the latter.

  The volumetric relay 63 is preferably designed and constructed so that the pressure in the outlet chamber 65 retains a predetermined relationship with that of the inlet chamber 61. For reasons of simplicity in the construction of the relay and ease of installation, testing and troubleshooting, we prefer that this relationship be linear and 1 to 1 ratio. We will also note that well

  that the bending of the diaphragm 71 causes small changes-

  momentary volume of gas defined by the first chamber 61, these changes are very small and have no significant effect on the characteristics of the device

2589261

  interface 10. Note that in the first realization

  tion of Figure 3, the confined volume 45 is that which is enclosed by the first chamber 61 of the volumetric relay

  63 and the part of buses 38, 59 which is to the right of the electro-

  valves 41, 43 in Figure 3. Other details of a type

  of volumetric relay 63 usable in the present invention

  tion are shown and described in the US patent

  No. 4,207,914 which is incorporated herein by reference.

  A second embodiment of the interface device 10 is partially shown in FIG. 4, and differs from the first embodiment only in that a reservoir 73 is connected in communication with the bus 59 with regard to the flow of the fluid. The volumetric dimension of the confined volume 45, or component "V" of the ideal gas equation, can be represented by the complex confined volume 45 as described in the first embodiment, or, as shown in FIG. 4, the complex volume 45 can include in addition that confined by the tank 73 coupled in parallel with

  the bus, as shown, or in series with it.

  It should be understood that the interface apparatus 10 can be easily configured using components of tubes, connectors, chokes, valves and

  existing volumetric relay. However, when quan-

  higher production rates are guaranteed, the ingredients

  can be brought together in a single structure

  in hydraulic passages and a confined volume of 45

  seated or otherwise formed therein.

  Although tool and design investments are necessarily increased with this latter approach,

  construction costs will be significantly reduced.

  When choosing the volumetric dimension

  of the confined volume 45, it is preferable to take into account

  sideration several theoretical parameters chosen in function

  tion of the characteristic equation of an ideal gas mention-

  born previously. One of these parameters is the value of the functional volume of compressed gas defined within

  this part of the interface apparatus 10 and kept sub-

"162589261

  stantially constant. Functional volume is volume

  total 45 of compressed gas confined as described in the first

  first embodiment, confined inside any reservoir 73 used and inside the first chamber 61, taken together with the volume of any parasitic gas. The parasitic gas is that which is found in the parts of the flow control means 33 located between a throttle 49 or

  51 and its associated solenoid valve 41 or 43, respectively.

  If the valves 41, 43 are constructed with throttles

  incorporated in them, this parasitic volume can be practi-

  Another important design parameter to consider

  derive is that each of the passages 57 in the throttles 49, 51, 53, 55 must in practice have a minimum diameter,

  on the order of 0.127 mm on average, in order to avoid obstruction

  tion of the passage by small particles entrained in the gas and in order to allow the manufacture of the throttles 49, 51, 53, 55 by means of conventional techniques at low cost. Another parameter also to be recognized is the leakage rate, if there is one, of the pneumatic connection points shown. This leakage rate can be reduced to a very low value or entirely eliminated by embedding the interface device 10 in a gas-impermeable compound after mounting. Another parameter to recognize also is the desired slopes of curves A, B which go

  result from the control of each of the valves 41, 43.

  In the case of an interface device 10 having connection points characterized by small but detectable leaks, the minimum size of the confined volume 45

  should preferably be such that it results in a change

  pressure relief in the gas contained inside the

  confined volume 45 less than approximately 1% during the inter-

  valle of maximum time during which the apparatus 10 will be maintained in a state of rest during which neither the valve 41 nor the valve 43 will be actuated. This normally constitutes the maximum time interval between the consecutive instants during which the control device of the system 27 takes a parameter, for example a temperature signal,

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  and generates correction orders. For optimal precision

  timale of the positioning of the cylinder over extended periods of operation, it is preferable that this pressure change is limited to half of 1%, or less. If the interface device 10 is coated to completely eliminate leaks from the connections, the determining parameter for the selection of the minimum content of the confined volume 45 becomes the maximum slopes desired for the curves A, B, calculated as a function of l 'equation mentioned above and minimum passage sizes available or which one wishes to use. We will also appreciate the fact that

  one of the aspects of the apparatus 10 is a device for

  glage which allows to select a slope for a particular part of the curve A which coincides with the slope of a part of the curve B, if one ignores their algebraic signs. In one embodiment of the invention, short lengths of pipe having an internal diameter of 1.588 mm and a total confined volume of approximately 1.311 cm3 were used

  to connect the solenoid valves 41, 43, a volumetric relay-

  plate 63 having a first chamber with a volume of approximately 2.13 cm3, and a reservoir 73, all of which are configured according to FIG. 4. In addition, the parasitic volumes of compressed gas total approximately 0.09832 cm3. For a first pressure source 35 regulated at a pressure of 1379 mb (20 psig), a passage of the first choke 49 adjusted to a calculated diameter of 0.1072 mm and a passage of the second choke 51 adjusted to a calculated diameter of 0.123 mm , we chose a volume content of 39.33 cm3, and this ensured excellent accuracy of the system for instants of temperature measurement spaced from each other by

about three minutes.

  If we then refer to Figures 3, 5, 6 and 7, a commercial embodiment of the apparatus 10 is shown, comprising a generally cylindrical cover 75, an upper body 77, a central plate 79 and a lower body 81. Bodies 77, 81, plate 79 and other parts

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  arranged inside these are formed in relation to each other so as to function as the volumetric relay 63 shown in Figure 5. A fluted central connection 83 is present for the connection of an air source 69 under pressure substantially

  aunt (Figure 3), while a connector arranged radially-

  ment (not shown) is provided for connection to the output bus 67 and the cylinder 25 of Figure 3. The plate 79 and the body 81 are internally configured so that the source 69 can also replace the source of Figure 3, the supply of the first inlet valve taking place via a small filter 85. The first inlet valve 41 and the second outlet valve 43 are constructed in a similar manner, and only the first inlet valve 41 will be described in detail. If reference is also made to FIGS. 8 and 9, the first inlet valve 41 comprises an inlet electromagnet 87, a control nozzle 89 and an extension 91 of a flexible lever 93 which is disposed between the electromagnet 87 and nozzle 89 for passing air in a controllable manner in the latter. The control nozzle 89 has a frustoconical upper section 95 and has a longitudinal passage 97 which passes through it and which is provided with a passage

* 99 order. In the preferred embodiment, and contrary-

  ment to the more common plastic passages 49, 51, 53, 55, having the previously described average minimum opening which passes through them, the passage 99 is formed of sapphire and has a nominal opening of 0.0762 mm which passes through it. By using a passage of this type, in which the air can flow

  relatively slowly, the physical size of the sub-

  stantially constant 45 can be reduced.

  If one refers more particularly to Figures 8, 9 and 10, a flexible lever 93 is shown, comprising a first extension 91 and a second extension 101, each extension 91, 101 being slightly movable towards

  the top when its associated electromagnet is energized.

  Each extension 91, 101 comprises a ferrous reinforcement element 103 and a lower valve button 105. In a preferred embodiment, the button 105 is produced under the

  form of a generally cylindrical box 107 in order to contain

  provide an elastic closure material 109, the box 107 having a lower opening 111 which passes through it to allow the material 109 to come into direct contact with the cone section 95. The lever 93 has a central opening 113 for receiving the extension of the assembly upright 115 of the upper body 77. Referring more particularly to FIG. 10, it is preferred that the assembly upright 117 and its extension 115 define between them a flange 119

  having an inclined surface, 4 being an angle of inclination

  favorite house. A preferred locking block 121 has an internal diameter sufficiently larger than the outside diameter of the extension 115 to freely fit thereon and define between them a small annular space. The external perimeter of the locking block 121 defines a rectangle whose dimension between the opposite edges is preferably slightly less than the diameter of the upright

  117, while the lower edge 123 of the locking block

  lage 121 is chamfered at a nominal angle, slightly higher than

  lower than that of ledge 119, by 10. When formed in this way, there will be two contact edges between the flange 123 of the locking block 121 and the lever 93, and a slight downward force will therefore be exerted on the extensions 91, 101, thus maintaining the valves

  41, 43 closed in the absence of power supply to the electromagnets.

  A fine spacer (not shown) can be inserted during assembly between each electromagnet, for example the electromagnet 87, and its associated extension 91, so as to create a thin film of air guaranteeing good closing of the valves, for example of the valve 41, when the electromagnet 87 is no longer supplied. The hold

is then removed.

  If we refer again to Figures 3, 4 and

  7, in a preferred embodiment, the substantial volume

  constant 45 air can be the volume 45 'which is

  confined between the upper body 77 and the cover 75. The reaction

  This way of volume 45 'eliminates the need to include a separate air tank 73 and allows for some manufacturing and size savings. As shown in Figure 6, the apparatus 10 can be suitably constructed so as to include a pair of fixing lugs 125 dimensioned and arranged so as to hang on the edges of a snap-on mounting slide (not shown)

  for ease of assembly and maintenance.

  Referring next to Figures 2 and 11, the electrical circuit of the preferred apparatus 10 can be designed with diodes 127, as shown, so that either

  the input electromagnet 87, i.e. the evacuation electromagnet

  cuation 129, can be powered from a direct digital control device 27 employing signals

reverse polarity.

  If we refer to the figures, and in the function-

  The digital control unit 27 of the system takes a signal representing a parameter to be controlled, like the signal from the thermostat 29 representing the actual temperature of the space, compares it with the value

  reference temperature in the database

  born, solves a predetermined algorithm and generates a digital control signal to actuate either the first valve 41 or the second valve 43. When the first valve 41 is opened, compressed gas will flow from the

  source 35 or 69, depending on the embodiment, by the first foreign

  glor 49 or passage 99, and the pressure inside the confined volume 45 or 45 ′ will increase by a value per unit of time determined by the parameters chosen as described above. The pressure in the first chamber 61 will therefore be such that it will exceed that in the second chamber 65, which causes the diaphragm 71 to bend to the right in FIG. 5. The end part of the piston 131 meeting the ball of control 133 will do

  leave the sealing edge 135 at the ball 133, provo-

  consequently the opening of the control valve, the surface of the opening being generally proportional to the degree of deflection of the diaphragm. Compressed air

  the source 69 will therefore be able to flow through the control valve

  to the second chamber 65, to the output bus 67 and to the transducer 25, until the pressure in the

  second chamber 65 reaches the value indicated by the report

  characteristic port of relay 63, that is to say here 1 of 1. The diaphragm 71 then returns to its equilibrium position

  and the control ball 133 returns to its closed position.

  flange 135. Any leakage of compressed gas in the outlet bus 67 connections will be detected by the

  volumetric relay 63 which will operate as described above

  known so as to maintain the pressure balance.

  Likewise, when the second valve 43 is actuated, the gas compressed in the confined volume, 45, 45 ′, is evacuated in a controllable manner by the second throttle 51 and by one or more chokers 53, 55, or as described in more detail. below, in the atmospheric ambient air. The pressure in the interface apparatus 10 will therefore decrease at a predetermined speed and the resulting pressure difference between the second chamber 65 and

  the first chamber 61 will cause the flexion of the diameter

  phrase 71 to the left in Figure 5. The movement of the

  diaphragm will allow the opening of passage 137 and the eva-

  controllable cuation of compressed gas in the second chamber

  , the output bus 67 and the transducer 25, in order to train

  again the pressures of the first chamber 61 and the second chamber 65 in their equilibrium relationship, after which the diaphragm 71 will move again to

close passage 137.

  It will be appreciated from the above that in the embodiments of the apparatus 10 shown in FIGS. 3 and 4, the size of the passages 57 in the throttles 53,

  , and the value of the confined volume 45 can be predicted-

  mined. Consequently, it is possible to choose restrictors 53 and / or having passage sizes which equalize the slopes (regardless of the sign) of the parts of curves A and

22 2589261

  B in which it is desired to operate a particular cylinder or group of cylinders, for example the

  parts between 206.84 and 551.58 mb (3 to 8 psig).

  If one of the restrictors 53 or 55 is not used, it can simply be plugged. In the embodiment of FIG. 7, the problem of the choice of exhaust restrictors is preferably solved by providing a pluggable and removable restrictor 139 which is dimensioned so as to adapt

  by sliding in the lower body, in sealing relation

  with this one. As the volume of complex air confined in the volume 45 ′ and the chamber 61 can be predetermined at the time of design and manufacture, the device can be supplied with a plurality of throttles 139,

  preferably three for a heating application,

  characteristic ventilation and air conditioning, each of them having a passage with a different cross-sectional area in order to produce curves A and B having substantially equal slopes for the pressure range, for example from 206.84 to 551.58 mb (3 to 8 psig), 551.58 to 896.32 mb (8 to 13 psig), or 896.32 to 1241.1 mb (13 to 18 psig) inside which one wishes to operate

the cylinder 25.

  The volumetric flow capacity of mini fluid

  male from sources 35 and / or 69 and the flow rate capacity

  gaseous of relay 63 can be determined from a

  known manner, and, in a preferred embodiment, these capa-

  volumetric flow and flow rate cities are chosen so that the pressure in the second chamber 65 and the outlet bus 67 coincides with that of the first chamber 61 without appreciable delay time between them. In addition, and in the case of the embodiments of Figures 3 and 4, it is preferable that the regulated pressure of the second source 69 is very close to that of the

first source 35.

  We will appreciate the fact that the interface device

  , when built according to the teachings of the

  vention, will provide to the cylinder of the transducer 25 a pressure which is a function of the duration of the signal applied to one of the valves 41, 43 by the control unit 27, and that this

  result is achieved without using feedback control.

  Therefore, the cylinder pressure will not be affected by the length of the bus 67 used to connect the trans-

  conductor 25 to the volumetric relay 63, nor by the function-

  ment of cylinder 25 itself, the enclosed volume of which changes

  throughout its displacement. Through selective use

  tive of chokes 53 and / or 55, or thanks to the choice of a choke-

  glor 139 suitable in the embodiment of Figure 7, the slope of the operational parts of the curves can also

be adjusted to the application.

  Although only a small number of embodiments of the invention have been illustrated and described, it should not be limited by them but only by the scope of

  the applicability of the appended claims.

24 2589261

Claims (3)

Claims   1. A pneumatic interface device for controlling treatment systems, characterized in that it comprises: pneumatic means (33) for controlling the flow rate to control the number of moles of a gas confined in a volume of gas substantially constant at first press; a volumetric relay (63) having a first chamber (61) coupled to said control means by a pneumatic bus (59) and further having a second   chamber (65) for coupling with a pneumatic transducer   tick to be controlled in position, said first cham-   bre and said second chamber being isolated from each other   with regard to the flow of the fluid, said relay provides   inserting into said second chamber a second pressure which has a predetermined relationship with said first pressure; a reservoir (73) coupled between said control means (33) and said relay (63), said bus, said relay and said reservoir cooperating so as to define said substantially constant volume of gas;   said flow control means (33) comprises   both means for adjusting the flow rate of said gas flowing from said substantially constant volume to an area at ambient pressure, said means for adjusting said flow rate comprising a pneumatic throttle (139)   having a flow passage having a first sur-   cross-section face, said choke being removable from said flow control means and being able to be replaced by a choke having a flow passage   having a second cross-sectional area.   2. Pneumatic interface device characterized in that it comprises in the form of a unit: a volumetric relay comprising an upper body (77), a central plate (79) and a lower body (81) defining with a diaphragm (71) a first inlet chamber (61) and a second outlet chamber (65) insulated from each other so that   relates to the flow of the fluid, said second chamber being in communication   cation with a source (69) of compressed gas via a control valve (63) controlled by said diaphragm   control means comprising an inlet valve (41) comprising   taking an electromagnet (87), a control nozzle (89) and an extension   segment (91) of a flexible lever (93) for controlling said nozzle, and a   drain valve (137) comprising an electromagnet (129), a valve   glor (51) and an extension (103) of a flexible lever (101) for controlling said choke a constant volume (45 ') confined between the upper body (77) and the cover (75): the air coming from the source (69) entering said constant volume via the nozzle (89) and leaving it via   through the choke (51) to an area at ambient pressure.   3. Apparatus] pneumatic interface according to claim 2, ca-   characterized by the fact that it further comprises a throttle (139) which can be inserted or removed to adjust the gas flow rate of said gas   volume confined to said zone at ambient pressure.